1. Field of the Invention
The invention relates to a method of producing a circuit module containing at least one chip containing an integrated circuit on a carrier. The invention furthermore relates to an integrated circuit module.
2. Description of the Related Art
Integrated circuits are usually produced by means of a multiplicity of photolithographic steps on a semiconductor substrate, normally a large number of such circuits being formed simultaneously on a relatively large-area semiconductor slice, a so-called “wafer”. After completion of the integration, the wafer is diced in order to obtain the individual circuits in the form of small “chips”. Each integrated circuit contains a plurality of contact areas, referred to hereinafter as “primary pads”, which are connected via individually assigned internal connection lines to other internal components of the circuit in order to transfer the electric currents and potentials required for operation.
Said pads form the connection points for the external connections of the integrated circuit to the outside world. Since the external connections cannot be miniaturized to the same extent as the integrated internal components, the pads must be relatively large in order to offer enough engagement area for the attachment of wires or for soldering connections.
A chip configured in the manner described above is positioned on the top side of a carrier, at which contact areas are situated, which are then electrically connected to the pads of the chip. For their part, said contact areas are connected to assigned contact pieces at the carrier, which contact pieces project at the underside of the carrier and can be formed as plug pins or as solder balls in order to fit or solder them together with corresponding mating contacts on a support.
There are two options for the relative orientation between chip and carrier when assembling these two parts. In order to describe the respective orientation, the side of the chip which is remote from the substrate and on which the primary pads are situated is referred to hereinafter as “front side”, while the opposite side, where the substrate is situated, is referred to as “rear side”.
The first option is a so-called “face-up” orientation. In this case, the chip is placed with its rear side downward onto the top side of the carrier, such that the primary pads are accessible for attaching connecting wires, the other ends of which are attached to the assigned contact areas of the carrier. In order to enable this “bonding”, the carrier contact areas are arranged on edge regions of the carrier which project laterally beyond the chip.
The second option is a so-called “face-down” orientation. In this case, the chip is placed with its front side downward onto the top side of the carrier, the contact areas being arranged on the underside of the carrier in such a way that they can be connected to the pads of the chip via wires through an opening in the carrier.
The decision as to which of the two possible orientations of a chip relative to the carrier in a circuit module to be chosen depends on various circumstances. Depending on the stipulations for the carrier, one orientation of the chip may be more favorable than the other in order to produce the conductive connections between the primary pads of the chip and the carrier. Another standpoint is whether the module contains only a single chip or a plurality of chips stacked one above another on the carrier. In the case of a single-chip module, face-down orientation may be preferable because conducting line paths that are as short as possible then result. In the case of a stacked module, however, face-up orientation may be more advantageous because it is simpler to wire the pads of all the chips with the carrier.
A manufacturer of circuit modules should therefore be flexible in the choice of chip orientation with regard to the carrier.